Vapor electric tube



J. SLEPIAN ETI AL Feb. 6, 1940.

VAPOR ELECTRIC TUBE Filed March 25, 1938 WITNESSES:

ATTORN EY .MKM

Pal-madre. s, 1940` i PATENT ori-'ICE VAPOR ELECTRIC, TUBE Joseph Slepian, Pittsburgh, and Leon R. Ludwig,

Wilkinsburg, Pa., assign ors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 25, 1938, Serial No. 198,070

6 Claims.

The invention relates rto electric discharge devices and especially vapor electric discharge devices.

An object of the invention is to provide a discharge device in which a greater amount of power can be converted by a tube of moderate size.

Another object oi.' the invention is to utilize as cathode materials substances which are solids at ordinary room temperatures.

Other objects and advantages of the invention will be apparent from the following description and drawing in which the single figure is a view partly in cross section and partly diagrammatic of a preferred embodiment of the invention.

A limitation of mercury arc glass tubes as at present constructed is that the mercury must be kept at a low temperature under 100 C. for satisfactory operation. Because of the poor thermal conductivity of the glass, the amount of power which can be converted by a tube of moderate size is very much limited.

The invention contemplates the utilization of other metals than mercury for the cathode material. These substances have a .low vapor pressure at high temperatures. In particular, the invention contemplates using bismuth, lead, cadmium, lithium and sodium which have a very much higher melting point than room temperatures. To this list might be also added caesium, rubidium and gallium which have a melting point intermediate that of room temperature and the melting point of the group above mentioned. The invention contemplates operating electric discharge devices utilizing the metals above mentioned or their alloys in definite temperature intervals above the ordinary ambient temperatures and accordingly special temperature controlling means is included in the invention.

In the drawing, I have disclosed a discharge device l preferably of a speciilc form having a -metallic cup shaped portion il containing the cathode material I2. The cup shaped portion has cylindrical sides I3 upon which the vaporized cathode material may condense and run down to the bottom portion of the cup il. The device also preferably has the sloping or curved top portion I4 connected to the sides I3. Material condensed on the portion I4 will either drop or run down to the bottom portion of the cup Il. Insulation i5 such as boro silicate glass is sealed to the top portion i4 and an anode lead-in portion i0. Anode l1 is connected to the metallic lead-in portion I8 preferably by screw (ci. 25o-21.5)

threaded connections i8 and i9. These portions are preferably hollow for the passage of the familiar make-alive extending therethrough from a. metallic portion 2| oi' the container wall sealed to insulation 22 such as boro silicate glass which is in turn sealed to the anode lead-in portion i6 of the container. I

Surrounding the discharge device is a casing 25 preferably of heat insulating material although the bottom portion 20 may be of conducting material if desired to make contact to the cup shaped portion il or a separate lead may extend through the casing to the cathode container. Inside of the casing is an electric heater 21 preferably connected through a thermostatic contact 28 to lines 29 for supplying electrical energy to the heating means. Another thermostat connection 30 is preferably connected in the lead 3i of the control electrode oi' the device which in the specic embodiment illustrated, is the make-alive 20. The casing also preferably has openings 32 which may be closed or opened by a relay 33 under the control of another thermostatic contact 34. This thermostatic contact 34 may also control the application of cooling means to the interior of the device such as the fan 35. The ian 35 may, of course, be under separate thermostatic control if desired.

It is desired that the temperature of the tube should be above the melting point of the cathode metal utilized. If bismuth, for example, is used, the temperature should be above 269 C. As disclosed in the drawing, the thermostatic contact 20 is closed to bring the device above this temperature and the thermostatic contact 30 to the control electrode has also closed, say at about 300 C., so that the device will start operating at this temperature. At 325 C. the thermostat 20 will open in order to interrupt the heating current through the coil 21 but this thermostat will reclose if the temperature drops to 300 C. If the temperature, however, increases, then at 350 the thermostat 34 will close and the current therethrough will open the Ventilating ports 32 and turn on the cooling fan 35. These ventilating openings may reclose at 325 C. and the fan shut ofi.

The provision for opening the Ventilating openings is to prevent especially too great a vapor pressure inside of the discharge device which may cause backilres.

'I'he heater 21 has been diagrammatically disclosed but is preferably so applied that the portions of the metal container wall on which the vapor substance from the cathode materialk I2 will condense, are 'above the melting point of lthe cathode.

If other materials than bismuth are utilized, the range of temperatures mentioned may be varied in accordance with the change in the melting point of the material. With tin, for example, the temperatures at which the thermostats are set may be lower than that for bismuth. .The example given is to be considered as illustrative only and not as specifically limiting theinvention to the material and temperature ranges mentioned. By using the device the tube is operated at a very much higher temperature than that possible with mercury vapor and accordingly much more power can be converted by a tube oi.' moderate size. In place of the elements mentioned, alloys of these materials may be utilized.

Many modifications may, of course, be made in the preferred embodiment without departing from the spirit of the invention. Accordingly, only such limitations are to be placed on the following claims as are necessitated by the prior art.

We claim as our invention:

1. A discharge device comprising a container, having the major portion of its wall-area of nontranslucent material, an anode and a cathode therein, said cathode being selected from the group of metals consisting of bismuth, lead, cadmium and tin,- and means maintaining the portion of said container having said cathode at a temperature between the melting point of said cathode and the temperature at Awhich the vapor pressure of said cathode would cause backires.

2. A discharge device comprising a container, having the major portion of its wall-area of nontranslucent material, an anode and a cathode therein, said cathode being selected from the group of metals consisting of bismuth, lead, cadmium and tin, and means maintaining the portion of said container having said cathode at a temperature between the melting point of said cathode and the temperature at which excessive vapor pressure is generated in said container.

3. A discharge device comprisinga container, an anode and a vaporizable cathode therein, said cathode being a solid at room temperatures, said container having interior surfaces for the condensing of cathode vapor .thereon and means maintaining said interior surfaces between themelting point of said cathode and the temperature at which the vapor pressure of said cathode would cause backnres.

4. A discharge device comprising a container, an anode and a vaporizable cathode therein, said cathode being a solid under 30 C., said container having interior surfaces for the condensing of cathode vapor thereon and means maintaining said interior surfaces between the melting point of said cathode and the temperature at which the vapor pressure of said cathode would cause backfires.

5. In combination, a discharge device comprisving a container, an anode, a control electrode and a vaporizable cathode therein, said cathode being of a material which is solid at room temperature, said container having interior surfaces for condensing the cathode vapor, and means maintaining said interior surfaces at temperatures between the melting point of said cathode and the temperature at which excessive vapor pressure is generated in said container, a circuit for said control electrode provided with means for preventing current flow in said device when said interior surfaces are at temperatures below the melting point of said cathode.

46. A discharge device comprising a container, an anode, a vaporizable cathode and an igniterelectrode contacting said cathode, said cathode being a solid at room temperature, said container having interior surfaces for condensing the vapor of said cathode, means for maintaining said interior surfaces at temperatures between the melting point of said cathode and the temperature at which excessive vapor pressure Y is generated in said container, and means for preventing the flow of current through said igniter-electrode when said interior surfaces are at temperatures below the melting point of saidgcathode.

LEON R. LUDWIG.

A JOSEPH SLEPIAN. 4s 

